Coal ash is disposed of in liquid form at large surface impoundments and in solid form at landfills. These residuals contain contaminants such as mercury, cadmium, and arsenic, which are related to cancer and other health effects.

The Environmental Protection Agency is presently deliberating whether to define coal ash as hazardous waste, and the Duke study’s authors stress that it’s important to look deeper than surface water to truly gauge its environmental ramifications. The US coal industry produces 130 million tons of coal ash each year. Close to one billion tons of coal ash is produced in the world each year. About 12% of the 7 billion tons of coal used each year ends up as coal ash.

The study comes as the EPA is considering whether to define ash from coal-burning power plants as hazardous waste. The deadline for public comment to the EPA was Nov. 19; a final ruling -- what Vengosh calls “a defining moment” -- is expected in coming months.

The study assessed water contaminant levels following a massive coal sludge spill in 2008 at a Tennessee Valley Authority power plant in Kingston, Tenn. Researchers collected more than 220 water samples over an 18-month period following the spill. They found that high concentrations of arsenic from the ash remained in water trapped within river-bottom sediment, called pore water, long after contaminant levels in surface waters returned to safe levels.

Samples of sediment extracted from 10 centimeters to half a meter below the surface in downstream rivers contained arsenic levels of up to 2,000 parts per billion. The EPA’s thresholds are 10 parts per billion for safe drinking water and 150 parts per billion for protection of aquatic life.

The potential impacts of pore water contamination extend far beyond the river bottom, he explains, because “this is where the biological food chain begins, so any bioaccumulation of toxins will start here.”

The TVA Kingston Fossil Plant coal fly ash slurry spill occurred just before 1 a.m. on Monday December 22, 2008, when an ash dike ruptured at an 84-acre (0.34 km2) solid waste containment area at the Tennessee Valley Authority's Kingston Fossil Plant in Roane County, Tennessee, USA. 1.1 billion gallons (4.2 million m³) of coal fly ash slurry was released. The coal-fired power plant, located across the Clinch River from the city of Kingston, uses ponds to dewater the fly ash, a byproduct of coal combustion, which is then stored in wet form in dredge cells. The slurry (a mixture of fly ash and water) traveled across the Emory River and its Swan Pond embayment, on to the opposite shore, covering up to 300 acres (1.2 km2) of the surrounding land, damaging homes and flowing up and down stream in nearby waterways such as the Emory River and Clinch River (tributaries of the Tennessee River). It was the largest fly ash release in United States history.

The take-away lesson is we need to change how and where we look for coal ash contaminants,” said Avner Vengosh, Duke professor of geochemistry and water quality and corresponding author of the study. “Risks to water quality and aquatic life don’t end with surface water contamination, but much of our current monitoring does.”

“At more than 3.7 million cubic meters, the scope of the TVA spill is unprecedented, but similar processes are taking place in holding ponds, landfills, and other coal ash storage facilities across the nation,” Vengosh said. “As long as coal ash isn’t regulated as hazardous waste, there is no way to prevent discharges of contaminants from these facilities and protect the environment.”

“It’s like cleaning your house,” Vengosh said. “Everything may look clean, but if you look under the rugs, that’s where you find the dirt.”

Mountaintop removal (MTR) mining involves the blasting off the tops of mountains to reach the coal seams below, with the millions of tons of former mountains pushed into stream valleys. MTR has buried nearly 2,000 miles of Appalachian streams, contaminated drinking water, impaired water quality for river recreation, increased water treatment costs for industry, displaced some communities, and increased susceptibility to flooding for others. An EPA environmental impact found that 724 miles (1,165 km) of Appalachian streams were buried by valley fills between 1985 to 2001, and that streams near valley fills from mountaintop removal contain high levels of minerals in the water and decreased aquatic biodiversity

MTR in the U.S. will mined over 1.4 million acres (5,700 km²) by 2010, an amount of land area that exceeds that of the state of Delaware. It occurs most commonly in West Virginia and Eastern Kentucky, the top two coal-producing states in Appalachia, with each state using approximately 1,000 tonnes of explosives per day for surface mining.

Coal sludge

Coal sludge, also known as slurry, is the liquid coal waste generated by washing coal. It is typically disposed of at impoundments located near coal mines, but in some cases it is directly injected into abandoned underground mines. Since coal sludge contains toxins, leaks or spills can endanger underground and surface waters.

There are over 1300 coal sludge impounds in the USA. Each one can be almost 3 square miles (1500 acres)

Heavy metals

Coal sludge also contains many heavy metals. Small amounts of heavy metals can be necessary for health, but too much may cause acute or chronic toxicity (poisoning). Many of the heavy metals released in the mining and burning of coal are environmentally and biologically toxic elements, such as lead, mercury, nickel, tin, cadmium, antimony, and arsenic, as well as radio isotopes of thorium and strontium.

Each year coal preparation creates waste water containing an estimated 13 tons of mercury, 3236 tons of arsenic, 189 tons of beryllium, 251 tons of cadmium, and 2754 tons of nickel, and 1098 tons of selenium

Mercury

Emissions from coal-fired power plants are the largest source of mercury in the United States, accounting for about 41 percent (48 tons in 1999) of industrial releases. According to the Centers for Disease Control and Prevention, eight percent of American women of childbearing age had unsafe levels of mercury in their blood, putting approximately 322,000 newborns at risk of neurological deficits. Mercury exposure also can lead to increase cardiovascular risk in adults. When mercury is deposited on land or in water, microorganisms convert part of it to a highly toxic form called methylmercury. When fish and animals eat these microorganisms, the toxins accumulate and can interfere with reproduction, growth, and behavior, and can even cause death

Coal Waste

Many of the heavy metals released in the mining and burning of coal are environmentally and biologically toxic elements, stored in federally unregulated coal waste sites Sulfur dioxide scrubbers also create coal waste. The flue-gas desulfurization (FGD) process creates a wet solid residue containing calcium sulfite (CaSO3) and calcium sulfate (CaSO4). Often dry material such as fly ash is added to stabilize the sludge for transport and landfill storage.

Note: the flue fas desulfurization is still needed otherwise the sulfur dioxide (smog) would go into the air and our lungs. So it is better to have air pollution control which creates the solid and liquid waste rather than have it end up in the air. It also goes to show how even when you are trying to control and prevent millions of deaths each year from air pollution you have to be careful with the toxic crap that is left over. 7 billion tons per year of burnable dirt is messy and deadly business.

Coal combustion waste is the nation's second largest waste stream after municipal solid waste. A power plant that operates for 40 years will leave behind 9.6 million tons of toxic waste

Water pollution, health risks, and regulations

As of June 2010, no federal regulations specifically govern the disposal of power plant discharges into waterways or landfills. Some regulators have used the Clean Water Act to try and limit pollution, but the law does not mandate limits on many dangerous chemicals in power plant waste, like arsenic and lead.

State officials sometimes place no limits on water discharges of arsenic, aluminum, boron, chromium, manganese, nickel or other chemicals that have been linked to health risks. According to a New York Times analysis of EPA records, 21 power plants in 10 states have dumped arsenic into rivers or other waters at concentrations as much as 18 times the federal drinking water standard. Only one in 43 U.S. power plants must limit how much barium is dumped into nearby waterways, despote being commonly found in power plant waste and scrubber wastewater and linked to heart problems and disease. EPA records indicate power plant landfills and other disposal practices have polluted groundwater in more than a dozen states, while a 2007 EPA report suggested that people living near some power plant landfills faced a cancer risk 2,000 times higher than federal health standards.

Power plants have often violated the Clean Water Act without paying fines or facing other penalties: ninety percent of 313 coal-fired power plants that violated the law since 2004 were not fined or otherwise sanctioned by federal or state regulators. And fines are often modest: Hatfield’s Ferry has violated the Clean Water Act 33 times since 2006, but has paid less than $26,000, even as the plant’s parent company earned $1.1 billion. According to the New York Times, after five states — including New York and New Jersey — sued Allegheny Energy to install scrubbers at one of its coal plants, the company began dumping tens of thousands of gallons of wastewater containing chemicals from the scrubbing process into the Monongahela River. The River provides drinking water to 350,000 people and flows into Pittsburgh.

In December 2009, there was a Congressional hearing in the House Energy and Commerce Subcommittee on "Drinking Water and Public Health Impacts of Coal Combustion Waste Disposal," largely in response to the 2008 TVA Kingston Fossil Plant coal ash spill and EPA reports on the health and environmental risks of coal ash and coal waste. Dr. Donald McGraw, the GOP's expert witness at the hearing, testified that arsenic is natural and coal waste benign